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From: Joao Moreira <joao@overdrivepizza.com>
To: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Sami Tolvanen <samitolvanen@google.com>, X86 ML <x86@kernel.org>,
	hjl.tools@gmail.com, Josh Poimboeuf <jpoimboe@redhat.com>,
	andrew.cooper3@citrix.com, LKML <linux-kernel@vger.kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	llvm@lists.linux.dev
Subject: Re: [RFC][PATCH 6/6] objtool: Add IBT validation / fixups
Date: Tue, 15 Feb 2022 15:38:33 -0800	[thread overview]
Message-ID: <4553dfb68285a686737969e117bf48cc@overdrivepizza.com> (raw)
In-Reply-To: <202202151503.91E9B76B@keescook>

>> 
>> Mostly so that we can deduce the address of the trap from the 
>> retpoline
>> site, also the above has a fairly high chance of using jcc.d32 which 
>> is
>> actually larger than jcc.d8+ud2.
> 
> Ah, yeah, that's an interesting point.
> 
> Still, I worry about finding ways to convinces Clang to emit precisely
> cmp/je/trap/call, but I guess we'll catch it immediately if it doesn't.
> :P

This can probably be done more easily/precisely if implemented directly
in the compiler's arch-specific backend. At least for x86 it wasn't a
hassle to emit a defined sequence of instructions in the past. The price
is that it will require a pass specific to each supported architecture,
but I guess this isn't that bad.

Perhaps this is discussion for a different mailing list, idk... but
just pointing that it is not a huge wall.

  reply	other threads:[~2022-02-15 23:38 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-22 17:03 [RFC][PATCH 0/6] x86: Kernel IBT beginnings Peter Zijlstra
2021-11-22 17:03 ` [RFC][PATCH 1/6] x86: Annotate _THIS_IP_ Peter Zijlstra
2021-11-23 13:53   ` Mark Rutland
2021-11-23 14:14     ` Peter Zijlstra
2021-11-24 18:18       ` Josh Poimboeuf
2021-11-22 17:03 ` [RFC][PATCH 2/6] x86: Base IBT bits Peter Zijlstra
2022-02-08 23:32   ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 3/6] x86: Add ENDBR to IRET-to-Self Peter Zijlstra
2021-11-22 18:09   ` Peter Zijlstra
2022-02-08 23:33     ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 4/6] objtool: Read the _THIS_IP_ hints Peter Zijlstra
2021-11-22 17:03 ` [RFC][PATCH 5/6] x86: Sprinkle ENDBR dust Peter Zijlstra
2021-11-23 14:00   ` Mark Rutland
2021-11-23 14:21     ` Peter Zijlstra
2022-02-08 23:38     ` Kees Cook
2021-11-22 17:03 ` [RFC][PATCH 6/6] objtool: Add IBT validation / fixups Peter Zijlstra
2021-11-24 19:30   ` Josh Poimboeuf
2022-02-08 23:43     ` Kees Cook
2022-02-09  5:09       ` Josh Poimboeuf
2022-02-09 11:41       ` Peter Zijlstra
2022-02-09 11:45         ` Peter Zijlstra
2021-12-24  2:05   ` joao
2022-02-08 23:42     ` Kees Cook
2022-02-09  2:21       ` Joao Moreira
2022-02-09  4:05         ` Kees Cook
2022-02-09  5:18           ` Joao Moreira
2022-02-11 13:38             ` Peter Zijlstra
2022-02-14 21:38               ` Sami Tolvanen
2022-02-14 22:25                 ` Peter Zijlstra
2022-02-15 16:56                   ` Sami Tolvanen
2022-02-15 20:03                     ` Kees Cook
2022-02-15 21:05                       ` Peter Zijlstra
2022-02-15 23:05                         ` Kees Cook
2022-02-15 23:38                           ` Joao Moreira [this message]
2022-02-16 12:24                         ` Peter Zijlstra
2022-02-15 20:53                     ` Peter Zijlstra
2022-02-15 22:45               ` Joao Moreira
2022-02-16  0:57               ` Andrew Cooper
2022-03-02  3:06               ` Peter Collingbourne
2022-03-02  3:32                 ` Joao Moreira
2022-06-08 17:53                 ` Fāng-ruì Sòng
2022-06-09  0:05                   ` Sami Tolvanen
2021-11-23  7:58 ` [RFC][PATCH 0/6] x86: Kernel IBT beginnings Christoph Hellwig
2021-11-23  9:02   ` Peter Zijlstra
2022-02-08 23:48 ` Kees Cook
2022-02-09  0:09 ` Nick Desaulniers

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